[父]{ちち} vs. [乳]{ちち} — father vs. breast Can one differentiate by pronunciation between []{} and []{} (as for and )? If not, does anyone have a reasonable explanation for why and have the same pronunciation? It seems unlikely that they stem from the same word, which was assigned two different characters, when were imported from China...

and cannot be differentiated by pronunciation (including accentation).

While the word titi "father" is attested in Old Japanese (8th century), titi "breasts" is not extant until the 17th century. However, it is more complicated than that. titi "breasts" is a reduplication of ti "breasts" which is extant in OJ. Also, titi "father" seems to be a reduplication of ti, a suffix attached to men. This can be seen in ooZI, hikoZI, and maro ga TI. The last one hints that ti may function as "father" on its own as well.

One possible motivation for ti > titi "father" is due to regularization with haha "mother", which repeats the same syllable twice. The ultimate etymology of both ti are unknown. Perhaps ti "father" is related to ti "blood" () as in what links a family. Other speculation is possible.