John Gill Commentary 1 Chronicles 4:14

"And Meonothai begat Ophrah: and Seraiah begat Joab the father of Ge-harashim; for they were craftsmen." — 1 Chronicles 4:14 (ASV)

And Meonothai
Another son of Othniel:

begat Ophrah; and Seraiah, the brother of Othniel, begat Joab ;
not David's general, but another of the same name, who lived long before him, see (1 Chronicles 2:54)

the father of the valley of Charashim :
of the inhabitants of the valley, or the prince of them, called the valley of craftsmen, (Nehemiah 11:35) the reason of which is here given:

for they were craftsmen ;
that dwelt in it, carpenters and smiths, both which the word signifies, men that wrought in stone, wood, and iron.