Does anyone know the name of this crochet stitch?

It's probably something like:

Ch 5 and join with sl st

Row 1: ch 4, dc into ring, *ch 2, dc, ch 1, dc, repeat from * 3 times, ch 2, join to first chain 4 with sl st.

Row 2: ch 3, dc into previous 2 ch space, *ch 1, dc into 1 ch space, ch 1, dc twice into 2 ch space, ch 1, dc twice into same 2 ch space, repeat from * three times. Ch 1, dc into 1 ch space, ch 1, dc twice into 2 ch space, ch 1 and join with sl st to first ch 3.

Row 3: ch 3, dc into previous 2 ch sp, ! ch 2, *dc into ch 1 space, ch 2, repeat from * twice. Dc twice into 2 ch space, ch 2, dc twice into same 2 ch space, repeat from ! 4 times and join with sl st.

That would be my guess, looking at the picture.

dont know if it has a particular name, but its a fairly common motif in many granny square and thread crochet pattern collections. you should be able to duplicate the square just from the picture.