milk (n.)youdaoicibaDictYouDict[milk 词源字典]
Old English meoluc (West Saxon), milc (Anglian), from Proto-Germanic *meluks "milk" (cognates: Old Norse mjolk, Old Frisian melok, Old Saxon miluk, Dutch melk, Old High German miluh, German Milch, Gothic miluks), from *melk- "to milk," from PIE root *melg- "to wipe, to rub off," also "to stroke; to milk," in reference to the hand motion involved in milking an animal (cognates: Greek amelgein, Latin mulgere, Old Church Slavonic mlesti, Lithuanian melžu "to milk," Old Irish melg "milk," Sanskrit marjati "wipes off"). Old Church Slavonic noun meleko (Russian moloko, Czech mleko) is considered to be adopted from Germanic.

Of milk-like plant juices from late 14c. Milk chocolate is first recorded 1723; milk shake is first recorded 1889, for a variety of creations, but the modern version is only from the 1930s. Milk tooth (1727) uses the word in its figurative sense "period of infancy," attested from 17c. To cry over spilt milk is first attested 1836 in writing of Canadian humorist Thomas C. Haliburton. Milk and honey is from the Old Testament phrase describing the richness of the Promised Land (Num. xvi:13, Old English meolc and hunie). Milk of human kindness is from "Macbeth" (1605).[milk etymology, milk origin, 英语词源]
spill (v.)youdaoicibaDictYouDict
Old English spillan "destroy, mutilate, kill," also in late Old English "to waste," variant of spildan "destroy," from Proto-Germanic *spilthjan (cognates: Old High German spildan "to spill," Old Saxon spildian "destroy, kill," Old Norse spilla "to destroy," Danish spilde "lose, spill, waste," Middle Dutch spillen "to waste, spend"), from PIE *spel- (1) "to split, break off" (cognates: Middle Dutch spalden, Old High German spaltan "to split;" Greek aspalon "skin, hide," spolas "flayed skin;" Lithuanian spaliai "shives of flax;" Old Church Slavonic rasplatiti "to cleave, split;" Middle Low German spalden, Old High German spaltan "to split;" Sanskrit sphatayati "splits").

Sense of "let (liquid) fall or run out" developed mid-14c. from use of the word in reference to shedding blood (early 14c.). Intransitive sense "to run out and become wasted" is from 1650s. Spill the beans recorded by 1910 in a sense of "spoil the situation;" 1919 as "reveal a secret." To cry for spilt milk (usually with negative) is attested from 1738. Related: Spilled; spilt; spilling.