What is the meaning of Hw-?

marks a third-person plural possessor; their

marks a third-person plural object of a postposition

alternative form of nhw- (second person plural possessor/second person plural object of a postposition)

Alternative form of ko-, a prefix that denotes a space or area. It appears lexicalized in numerous nouns and compounds, as well as in directional terms.

alternative form of ho- (fourth person/spatial object prefix).

Source: wiktionary.org