What is the origin of the phrase ‘sleep tight’?
短语sleep tight的由来
It seems that tight in this expression is the equivalent of the only surviving use of the adverb tightly meaning 'soundly, properly, well, effectively'. The 20-volume historical Oxford English Dictionary labels this adverb 'now dialectal'.
看起来，这是形容词tight用作副词tightly的一种用法，也是tightly幸存至今的一个词义。副词tightly曾经表示“完好地、恰当地、很好、有效地”这一词义，但已经不用了。而短语sleep tight和blow me tight中仍保留了这一副词词义，主要用于口语中。Sleep tight是一种传统的押韵方式，是睡前的口语，表示“睡个好觉”；而blow me tight表示因愤怒而恼火的一种诅咒，例如Blow me tight if ever I saw such a thing in my life before.
