Tom, Dick and ... Jack in the OED and in Sonnet 128

The Oxford English Dictionary defines more than 30 meanings of the word "jack", but ignores the obscene meaning which is attested to by numerous puns in Elizabethan and Jacobean literature. The associations which are particularly evoked by the term "virginal jacks" for the bouncing wooden sticks inside the mechanisms of that keyboard instrument (often played by young girls), must be taken into account in any readings of Shakespeare's Sonnet 128, where the speaker is jealous of the "jacks" which are tickling the palms of his musical beloved.