Every English thesaurus lists quite a few synonyms for the adverb besides. These include also, too, as well, moreover, furthermore, what’s more, in addition, additionally and over and above that. Some of these have Scots equivalents such as tae (too), as weel (as well) and whit’s mair (what’s more) but Scots can make a contribution to the list that is all of its own.
The word is forby, pronounced with the emphasis on the second syllable. Formed, as you might expect, from the words for and by, forby has its origins in Middle English. It was formerly to be found in English as well as Scots, but now its use in English is confined to certain dialects. Forby has the alternative spelling forbye, which sometimes becomes forbyes, although this is now rather old-fashioned.
As indicated above, the adverb forby means in addition, as in The weather forecast said it would be fine, but it was rainin’ and cauld (cold) forby. and as in Heinjured baith (both) his arms in the accident and broke a leg forby.
Forby can also be a preposition with meanings corresponding to those of the adverb. Thus it means in addition to or as well as, as in I kent (knew) a few there forby the hosts. and as in The flat was poky, filthy and damp forby.
Rather confusingly, forby as a preposition can also mean except or apart from, as in Forby the family, there were nae (no) mourners at the auld (old) man’s funeral. And as in We loved the place forby the weather. Forby can also be used to mean let alone, much less when used in such constructions as The flat’s no big enough for the kids, forby guests.
Forby as a preposition can also be used to mean compared with or relative to, as in in The hooses (houses) on the estate were quite sizable, but really tiny forby the laird’s palatial place.
Forby has some meanings that seem to have become more popular in Ulster Scots than they did in the home-made variety. Ulster Scots came into being when the Scots language was taken to Ulster in the early part of the 17th century by the large number of Scots who settled there under the Plantation policy of King James VI and I. By means of this policy of colonisation of parts of Ireland the king hoped to quell the rebellious Irish.
Of these meanings of forby that became more common in Ulster one is its use as an intensifying adverb, meaning extraordinarily or unusually, as in He was a huge, strong man, but he was forby gentle. The other is forby as used as an adjective meaning uncommon, extraordinary, unusually good, as in It’d take a forby man to take on that task.
One more thing. Should you be described as being forby yirsel it means that you are out of your mind. It’s a bit like being beside yourself, but even worse.