Tenth day or day ten. No matter how you look at this word, it makes a lot of sense.

Words that count days use an exceptional reading. Even though this is a jukugo word, it actually uses kun’yomi readings. Think about this word this way:

This marks the tenth day since this talker (とおか) began talking non-stop. Talkers love talking, but this one is getting quite unbearable… Ten days of talking, can you believe it?

Note that とお, generally pronounced "toh" with a long "o" sound, is not a common spelling, and you’ll only see it with a handful of kanji and vocabulary, like in this case. I mean, how often do you encounter a talker who can go on non-stop for ten days? That's pretty rare, right?