'Bunting tosser' or 'Bunts' is an informal term used in the Royal Navy to describe the sailors who hoist signal flags. Although dating from the period of signalling by flags [1], it has survived as a general term for naval signallers.[2] Wireless operators may also be termed 'sparkers'.
Bunting is now a commonplace term for any small decorative flags or streamers strung on a line, but its original etymology is more specific as the worsted cloth used for flags in the Navy.
The term doesn't appear in Covey Crump, although that's a far from infallible source.[3]
Although a naval term, 'bunting tosser' is known across the services and may be used as a jocular insult amongst Army signallers, the implication being that the person addressed is only fit for the Navy.[4]