Yester-day, I did an-other Duolingo lesson in Esperanto (lesson 3 in Verbs: Past & Future). I learned the words for yester-day (hieraŭ), to-day (hodiaŭ), and to-morrow (morgaŭ). I think the words themselves will be pretty easy to learn because they're cognates with yester-day, to-day, and to-morrow in languages I already know, but the etymologies bother me.
I lookt up all of these words on wiktionary to confirm the etymologies I suspected. Hieraŭ and hodiaŭ come from Latin. Hieraŭ comes from heri (indirectly via the French hier), and hodiaŭ comes from hodie. But morgaŭ comes from the German Morgen.
Because these three words are so closely related, it would have made sense for all of the Esperanto words to come from the same language. That they don't seems incongruous.
