Travail is “painfully difficult or burdensome work”, “suffering resulting from mental or physical hardship”, or “the pain of childbirth”. As a verb, travail means “to suffer the pangs of childbirth” or “to toil or exert oneself”.
The word comes from French, but it can be traced back to Latin tripalium, a torture device. According to the Online Etymology Dictionary, the word tripalium is “probably from L. tripalis ‘having three stakes’ (from tria, tres ‘three’ + palus ‘stake’), which sounds ominous, but the exact notion is obscure.”
Those Romans had it right, though: work is definitely a form of torture. So is childbirth. (I so don’t want to have kids!)
But anyway, travail is a useful word. It isn’t particularly common, but it isn’t obscure, either. It’s just specific. If you’re travailing, you’re not just working or toiling; you’re also being tortured! (Again, childbirth. Ouch.)