means A saw is a tool with a toothed blade for cutting through wood, metal, or bone — and also, separately, the past tense of 'see' and an old word for a wise saying.

from From Old English 'sagu' (the cutting tool), tied to a root meaning 'to cut' — a cousin of Latin 'secare,' which also gives us 'section' and 'scissors.' The 'saw' meaning 'a wise saying' (as in 'old saws') is a different Old English word, 'sagu,' related to 'say' and 'saga' — a thing spoken. And 'saw' as the past of 'see' comes from Old English 'seah.' Three separate words that happened to grind down to the same three letters.