Take the tour ×  Is it known why a さかや normally has a か, rather
than a け like in さけ?  Are there many other -や constructions for
stores that change the spelling of the word added to?
share|improve this question add comment  1 Answer  up vote 26
down vote accepted  (Especially in the ancient times,) there
were/are bound morphemes (morphemes that cannot be used in
isolation as a word) that end with the vowel a. The a at the end
of these morphemes cannot appear at a word boundary. These forms
are known as 露出形.  saka- (as in 酒) ama- (as in 雨) puna- (as in
船) ma- (as in 目)  When they are used as the first component of a
compound noun, the a-ending is rescued by being attached to the
second component:  sakaya (酒屋), sakagura (酒蔵), sakadaru (酒樽),
sakamori (酒盛り), sakazuki (盃) amaoto (雨音), amagasa (雨傘), amagappa
(雨合羽), amayadori (雨宿り) funatsukiba (船着き場), funanori (船乗り),
funazumi (船積み), funabashi (船橋), funayoi (船酔い) mabuta (目蓋),
manako (眼)  These morphemes cannot be used in isolation, but
there were ways to modify them