Abarim Publications' online Biblical Hebrew Dictionary
These two nouns are probably loan words from other languages and not related in any demonstrable way. Their similarity is probably a coincidence:
The masculine noun סיר (sir I) means pot. This word exists in Arabic as well and even in Greek, as σιρος (siros), denoting a pit or vessel to keep corn in.
Our noun is used for household boiling pots (Exodus 16:3, 2 Kings 4:38, Zechariah 14:21) as well as for the holy vessels of the tabernacle (Exodus 27:3) and temple (1 Kings 7:40, 2 Kings 25:14).
The masculine noun סיר (sir II) means thorn (Isaiah 34:13, Hosea 2:8, Ecclesiastes 7:6), or hook (Amos 4:2). Another word for hook is וו (waw).