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acrobat [acrobat 词源字典]: acrobat: [19] The Greek adjective ákros meant ‘topmost, at the tip or extremity’ (it derives ultimately from the Indo-European base *akmeaning ‘be pointed or sharp’, which also gave rise to acid, acute, oxygen, and edge). It crops up in acrophobia ‘fear of heights’; in acropolis ‘citadel’, literally ‘upper city’; in acromegaly ‘unnaturally enlarged condition of the hands, feet, and face’, literally ‘large extremities’; and in acronym, literally ‘word formed from the tips of words’. Acrobat itself means literally ‘walking on tiptoe’.

The -bat morpheme comes from Greek baínein ‘walk’, which is closely related to basis and base, and is also connected with come. Akrobátēs existed as a term in Greek, and reached English via French acrobate.
=> acid, acute, edge, oxygen[acrobat etymology, acrobat origin, 英语词源]
accidentally (adv.): late 14c., "non-essentially," also "unnaturally," from accidental + -ly (2). Meaning "unintentionally" is recorded from 1580s; phrase accidentally on purpose is recorded from 1862.
unnatural (adj.): early 15c., "not in accord with physical nature," from un- (1) "not" + natural (adj.). Meaning "artificial" is attested from 1746; that of "at variance with moral standards" is from 1520s. Related: Unnaturally; unnaturalness.
Procrusteanize: "To enforce uniformity or conformity without regard to natural variation or individuality; to stretch or contract unnaturally", Mid 19th cent.; earliest use found in Joseph Worcester (1784–1865), lexicographer and author. From Procrustean + -ize.