Bob's-a-dyingn.

Etymology: Apparently < Bob's a dying, the title of a lively sailors' song popular in the first half of the 19th cent. (although this is first attested slightly later) < Bob , pet form of the male forename Robert (see Bob n.⁷) + 's , contracted form of is (3rd singular present indicative of be v.) + a prep.¹ (compare sense 11a at that entry) + dying n.With the song title compare the following:1833 Monthly Mag. Feb. 628 ‘Man the haulyards—let go reef-tackles, cluelines, buntlines—light up in the top—hoist away!’ Up they went to the tune of ‘Bob’s a dying’.1836 Metropolitan Mar. 134/1 I could dance a hornpipe and kick up Bob's a-dying.1854 Notts. Guardian 29 June 5/4 The bridal party marched in regular order next, and over them a parasol, attached to a long rod of iron, was carried by another man, and by his side was an accordeon player, striking up some lively strains, such as ‘Pop goes the Weasel’, ‘Bob’s a dying’, &c. The β. and γ. forms show respectively (apparently arbitrary) alteration and shortening; with the form bobs-a-dilo at β. forms perhaps compare O int. 3.