Here are a couple compound words that end with 乎:
热乎,温乎 温乎,確乎 確乎,玄乎 玄乎,忙乎 忙乎,晕乎 晕乎,近乎 近乎,热乎乎 热乎乎,傻乎乎 傻乎乎.
Is there an understanding of how 乎 became used in these words? Does it have any relation to the classical usage of 乎 as an interrogative marker?