This morning in my Spanish class, I learnt that “estoy constipada” means “I have a cold”. Talk about false friends. So how did this word come to take a different meaning in English and in French? Its etymology reveals all:

[Latin cōnstīpāre, cōnstīpāt-, to crowd together : com-, com- + stīpāre, to cram.]

So originally, it denotes a crowding, which became restricted to the intestine in English and in French, and to the nose in Spanish. This is the result of a very quick search, if anyone has more information, I’d love to hear it.