Unit
来自Big Physics
late 16th century (as a mathematical term): from Latin unus, probably suggested by digit.
wiktionary
Formerly unite, a later form of unity; see unity.
etymonline
unit (n.)
1560s, "single number regarded as an undivided whole," alteration of unity on the basis of digit. Popularized in John Dee's English translation of Euclid, to express Greek monas (Dee says unity formerly was used in this sense). Meaning "single thing regarded as a member of a group" is attested from 1640s. Extended sense of "a quantity adopted as a standard of measure" is from 1738. Sense of "group of wards in a hospital" is attested from 1893.
