Wouldn't it be nice a world without aches?!!! Nice to meet you too :)

Thanks for the detailed explanation, JacquiD!.Hopefully, one day "aches" will not exist and we won't need official collocations to express them :) However, I am really glad to meet you :)

Oops tab got stuck! sorry!

Well you might have a 'legache' but we don't call it that of course. 'Head' and 'ache' is a collocation that always goes together like toothache, backache and stomach ache. If we want to express the same idea with other parts of the body we have to use full sentences as the collocations don't exist. 'My leg aches'. or 'My leg hurts'. Historically 'headache' is the oldest of the collocations with 'ache' dating back to before 1000. Toothache is almost just as old (before 1050) but backache and stomach ache are relatively new collocations (1600s and 1700s respectively) So you never know if people use it enough we may one day have 'legache' as an official collocation!

Well you might have a 'legache' but we don't call it that of course. 'Head' and 'ache' is a collocation that always goes together like toothache, backache and stomach ache. If we want to express the same idea with other parts of the body we have to use full sentences as the collocations don't exist. 'My leg aches'. or 'My leg hurts'. Historically 'headache' is the oldest of the collocations with 'ache' dating back to before 1000. Toothache is almost just as old (before 1050) but backache and stomach ache are relatively new collocations (1600s and 1700s respectively) So you never know if people use it enough we may one day have 'legache' as an official collocation!