_Ennui_ (Vol. vii., p. 478.).--
"Cleland (voc. 165.) has, with his usual sagacity, and with a great
deal of trouble, as he himself acknowledges, traced out the true
meaning and derivation of this word: for after he had long despaired of
discovering the origin of it, mere chance, he says, offered to him what
he took to be the genuine one: 'In an old French book I met,' says he,
'with a passage where the author, speaking of a company that had sat up
late, makes use of this expression, "l'ennuit les avoit gagnes," by the
context of which it was plain he meant, that the common influence of
_the night_, in bringing on _heaviness_ and _yawning_, had come upon
them. The proper sense is totally antiquated, but the figurative
remains in full currency to this day."--Lemon's _Etymological
Dictionary_.
The true synonym of _ennui_ seem to be _taedium_, which appears to have the
same relation to _taedo_, a torch, as _ennui_ to _nuit_.