colloquial or familiar abbreviation of the masc. proper name Jacob (q.v.). As the typical name of a rustic lout, from 1854. (Jakey still is the typical name for "an Amishman" among the non-Amish of Pennsylvania Dutch country). Slang meaning "excellent, fine" is from 1914, American English, of unknown origin.
Excellent; very satisfactory; hunky-dory: She said the whole college seemed jake to heradverb
: You never can tell on a day like this, things could be goin' jake one minute, then presto, before you know it you're history
[1914+ Underworld; origin unknown]