Little fun-fact: We still have a trace of this left in Norwegian, where the most common way to say “1.5” is not “en og en halv” (“one and a half”) but “halvannen” which roughly translates to “half second”.
We abandoned the “half third”, “half fourth” etc. very long ago (if we ever used them), but “halvannen” just rolls nicely off the tongue.
You also use halv tres (50) and halv firs (70) don’t you?