mickey

Alternative letter-case form of Mickey (noun), from Mickey (“diminutive of the male given name Michael”, proper noun), from Mick (“diminutive of the male given name Michael”) +‎ -ey (a variant of -y (diminutive suffix)).

Noun sense 1 (“smallest distance that a computer mouse can move a cursor”) refers to the cartoon character Mickey Mouse.

Noun sense 5 (“penis”), noun sense 7.1 (“Irishman”), and noun sense 7.2 (“potato; sweet potato”) refer to the fact that since the 17th century Michael and its diminutives Mick, Mickey, and Mike have been one of the most common names in Ireland, and to the prevalence of potatoes in the Irish diet; compare murphy (“potato”).

Noun sense 6.2 (“in take the mickey: (false) pride”) possibly refers to the use of Mickey Bliss as rhyming slang for piss (“act of urinating”); compare take the piss