A randan is a boat rowed by three persons, stern and bow using a single oar each and the central person a pair of sculls. The word is of unknown origin, and can hardly be connected with a slang term for a row or spree, which is found as early as the beginning of the 18th century and is generally taken as a variation of random, haphazard.
Additionally in Scotland, the term out on the randan describes a night of drinking and/or socialising.
For example - "Awrite boys, gawn oot oan the randan the nite ?" or "Aw man, ah wis pure fleein' oot ma nut oan Friday an' ah goat a weekender 'cause ah wis talkin' tae ma shadow and the polis startid hasslin' us, so 'cause am pure plasamed oot ma dome ah start trying tae get wide wi them, so the done us fur breach, but got away wi th poss charge cause ah'd gubbed thum aw. But ah'm tellin' ye's boys, that's it fur me gawn oot oan the randan, ah'm pure done wi it man, it's fryin' ma dome man."