late 12c., mēk, "gentle or mild of temper; forbearing under injury or annoyance; humble, unassuming;" of a woman, "modest," from a Scandinavian source such as Old Norse mjukr "soft, pliant, gentle," from Proto-Germanic *meukaz (source also of Gothic muka-modei "humility," Dutch muik "soft"), a word of uncertain origin, perhaps from PIE *meug- "slippery, slimy." In the Bible, it translates Latin mansuetus from Vulgate (for which see mansuetude). Sense of "submissive, obedient, docile" is from c. 1300.
"tedious and ineffectual person," 1935, American English carnival slang, of uncertain origin. Perhaps from jerkwater "petty, inferior, insignificant" [Barnhart, OED]; alternatively from, or influenced by, verbal phrase jerk off "masturbate" [Rawson]. The lyric in "Big Rock Candy Mountain," sometimes offered as evidence of earlier use, apparently is "Where they hung the Turk [not jerk] that invented work."
A soda-jerk (1915; soda-jerker is from 1883) is so called for the pulling motion required to work the taps.
The SODA-FOUNTAIN CLERK
Consider now the meek and humble soda-fountain clerk,
Who draweth off the moistened air with nimble turn and jerk,
[etc., Bulletin of Pharmacy, August, 1902]
"apt or dexterous, subtly clever or skillful," mid-15c., from Old English gedæfte, which meant "mild, gentle, simple, meek," but which splintered into different forms and senses in Middle English, yielding this word and also daft (q.v.). In Middle English it also could mean "well-mannered, gentle, modest, mild," and "dull, uncouth, boorish." Cognate with Gothic gadaban "to be fit," Old Norse dafna "to grow strong," Dutch deftig "important, relevant," from Proto-Germanic *dab-, which has no certain IE etymology and is perhaps a substratum word. Related: Deftness.
In Middle English, used of the weather. Current sense of "easily flexible" is from c. 1300. Related: Litheness. Old and Middle English had the related verb lin "to cease doing (something)," also used of the wind dying down.