please (v.)youdaoicibaDictYouDict[please 词源字典]
early 14c., "to be agreeable," from Old French plaisir "to please, give pleasure to, satisfy" (11c., Modern French plaire, the form of which is perhaps due to analogy of faire), from Latin placere "to be acceptable, be liked, be approved," related to placare "to soothe, quiet" (source of Spanish placer, Italian piacere), possibly from PIE *plak-e- "to be calm," via notion of still water, etc., from root *plak- (1) "to be flat" (see placenta).

Meaning "to delight" in English is from late 14c. Inverted use for "to be pleased" is from c. 1500, first in Scottish, and paralleling the evolution of synonymous like (v.). Intransitive sense (do as you please) first recorded c. 1500; imperative use (please do this), first recorded 1620s, was probably a shortening of if it please (you) (late 14c.). Related: Pleased; pleasing; pleasingly.

Verbs for "please" supply the stereotype polite word ("Please come in," short for may it please you to ...) in many languages (French, Italian), "But more widespread is the use of the first singular of a verb for 'ask, request' " [Buck, who cites German bitte, Polish proszę, etc.]. Spanish favor is short for hace el favor "do the favor." Danish has in this sense vær saa god, literally "be so good."[please etymology, please origin, 英语词源]
pleased (adj.)youdaoicibaDictYouDict
"satisfied, contented," late 14c., past participle adjective from please (v.).
pleaser (n.)youdaoicibaDictYouDict
1520s, agent noun from please.
pleasurable (adj.)youdaoicibaDictYouDict
1570s, from pleasure (n.) + -able. Related: Pleasurability; pleasurably. For sense, compare comfortable.
pleasure (n.)youdaoicibaDictYouDict
late 14c., "condition of enjoyment," from Old French plesir, also plaisir "enjoyment, delight, desire, will" (12c.), from noun use of infinitive plaisir (v.) "to please," from Latin placere "to please, give pleasure, be approved" (see please (v.)). Ending altered in English 14c. by influence of words in -ure (measure, etc.). Meaning "sensual enjoyment as the chief object of life" is attested from 1520s.
pleasure (v.)youdaoicibaDictYouDict
1530s, "to take pleasure in;" 1550s as "give pleasure to," from pleasure (n.). Sexual sense by 1610s. Related: Pleasured; pleasuring.
pleasure-seeker (n.)youdaoicibaDictYouDict
from pleasure (n.) + agent noun from seek.
pleat (v.)youdaoicibaDictYouDict
1560s, used as the verb version of plait (n.) and probably representing an alternative pronunciation. Related: Pleated; pleating.
pleat (n.)youdaoicibaDictYouDict
"a fold," 1580s, variant of plait (n.). With a gap in the printed record 17c.-18c., but probably it was in continuous oral use.
pleather (n.)youdaoicibaDictYouDict
by 1991, from plastic + leather.
pleb (n.)youdaoicibaDictYouDict
1856 as a colloquial shortening of plebeian in the ancient Roman sense. West Point sense attested by 1851 (see plebe).
plebe (n.)youdaoicibaDictYouDict
also pleb, "member of the lowest class at a U.S. military academy," 1833, probably a shortened form of plebeian "one of the lower class," which in Latin also had the short form plebs or plebes.
plebeian (n.)youdaoicibaDictYouDict
"member of the lowest class," 1530s, from Latin plebius "person not of noble rank," from adjective meaning "of the common people" (see plebeian (adj.)).
plebeian (adj.)youdaoicibaDictYouDict
also plebian, "of or characteristic of the lower class," 1560s in a Roman historical sense, from Latin plebeius "belonging to the plebs," earlier plebes, "the populace, the common people" (as opposed to patricians, etc.), also "commonality; the mass, the multitude; the lower class," from PIE *ple- (see pleio-). In general (non-historical) use from 1580s.
plebiscite (n.)youdaoicibaDictYouDict
"direct vote of the people," 1860 (originally in reference to Italian unification), from French plébiscite (1776 in modern sense, originally with reference to Switzerland), from Latin plebiscitum "a decree or resolution of the people," from plebs (genitive plebis) "the common people" (see plebeian (adj.)) + scitum "decree," noun use of neuter past participle of sciscere "to assent, vote for, approve," inchoative of scire "to know" (see science). Used earlier (1530s) in a purely Roman historical context. Related: Plebiscitary.
plectrum (n.)youdaoicibaDictYouDict
something used to pluck the strings of a musical instrument, 1620s, from Latin plectrum, from Greek plektron "thing to strike with" (pick for a lyre, cock's spur, spear point, etc.), from plek-, root of plessein "to strike" (see plague (n.)).
pledyoudaoicibaDictYouDict
past tense and past participle of plead (v.).
pledge (v.)youdaoicibaDictYouDict
c. 1400, "to promise" (something to someone), "to give over as security for repayment," also "promise faith to," from pledge (n.) and from Old French plegier, from plege (n.). From mid-15c. as "to stand surety for, be responsible for;" late 15c. as "to mortgage." Meaning "put (someone) under oath" is from 1570s; sense of "to solemnly promise or guarantee" is from 1590s, as is sense "to drink a toast." Related: Pledged; pledging.
pledge (n.)youdaoicibaDictYouDict
mid-14c., "surety, bail," from Old French plege (Modern French pleige) "hostage, security, bail," probably from Frankish *plegan "to guarantee," from *pleg-, a West Germanic root meaning "have responsibility for" (cognates: Old Saxon plegan "vouch for," Middle Dutch plien "to answer for, guarantee," Old High German pflegan "to care for, be accustomed to," Old English pleon "to risk the loss of, expose to danger;" see plight (v.)).

Meaning "allegiance vow attested by drinking with another" is from 1630s. Sense of "solemn promise" first recorded 1814, though this notion is from 16c. in the verb. Weekley notes the "curious contradiction" in pledge (v.) "to toast with a drink" (1540s) and pledge (n.) "the vow to abstain from drinking" (1833). Meaning "student who has agreed to join a fraternity or sorority" dates from 1901.
Pleiades (n.)youdaoicibaDictYouDict
late 14c., the seven daughters of Atlas and Pleione, transformed by Zeus into seven stars, from Latin Pleiades, from Greek Pleiades, perhaps literally "constellation of the doves" from a shortened form of peleiades, plural of peleias "dove" (from PIE root *pel- "dark-colored, gray"). Or perhaps from plein "to sail," because the season of navigation begins with their heliacal rising.

Old English had the name from Latin as Pliade. Mentioned by Hesiod (pre-700 B.C.E.), only six now are visible to most people; on a clear night a good eye can see nine (in 1579, well before the invention of the telescope, the German astronomer Michael Moestlin (1550-1631) correctly drew 11 Pleiades stars); telescopes reveal at least 500. Hence French pleiade, used for a meeting or grouping of seven persons.