straight-laced

Where it comes from

Widely agreed to have originated (centuries ago) by homophonic confusion (in speech) of strait-laced (“tight-laced”), but long since so widely accepted and used, because of having such strongly apparent analogy with straight in its senses relating to orthodoxy and conformity (compare squareness), that it can no longer accurately be called erroneous; instead it is an established alternative form with its own reanalyzed surface analysis. Compare straitjacket with *straightjacket; the latter is still usually regarded as an error, but the relationship is analogous. Compare also strait and narrow with straight and narrow, where the latter spelling has all but replaced the former.