primary meaning of ‘boggle’ was ‘to start with fright’, originally with reference to horses—probably related to the nouns ‘bogle’ and ‘bogey’, denoting an evil spirit such as horses are reputed to see
meaning: everything is or will turn out all right—Scotland, 1891—‘bob’ probably related to the adjectives ‘bob’ and ‘bobbish’, meaning ‘well, in good health and spirits’
to be insane—late 19th century—originated in the fact that in 19th-century productions of Shakespeare’s ‘Hamlet’, Ophelia appeared with straws in her hair in her ‘mad scene’
‘to know where the bodies are buried’: to have personal knowledge of the secrets or confidential affairs of an organisation or individual—USA, 1928, as ‘to know where the body is buried’
‘to be unable to run a whelk stall’ and variants: to be incapable of managing the simplest task or enterprise—coined by John Elliot Burns (1858-1943), English trade unionist and politician, in the 1894 New Year’s address to his constituents of Battersea
1808, as ‘to talk a horse’s hind leg off’—‘[animal’s] hind leg off’ is probably a hyperbolic extension of ‘to talk’, emphasising the speaker’s persistence or eloquence
British, 1925—‘to throw a spanner in(to) the works’: to cause disruption, to interfere with the smooth running of something—synonym (American English): ‘to throw a monkey wrench into’
The original image was of throwing a monkey wrench into the cylinder of a threshing machine, and was exclusively applied to political situations—USA, late 19th century.