1366: merry and mirth Sep 7, 2018
One of the reasons oft cited for the maintenance of English's inconsistent orthography is history, and while this leads to clues of etymology that would otherwise be difficult to recognize, sometimes it is less helpful. For instance, the word 'merry' is related to the word 'mirth'. Think about the meaning this should seem reasonable, and moreover, 'merry' is an adjective with an adjectival suffix, and seeing a noun with a nominal suffix from the same root should make sense. However, the spelling is not indicative of this, making the confusing spelling in English have less significance perhaps.