Meaning: intimately known
Rewrite 1: know it like the moles1 on my chest
Rewrite 2: know it like the frown lines on my (spouse's) forehead
Rewrite 3: know it like the scent of my (lover's) favorite perfume
Rewrite 4: could recognize it in a crowd like a mother bird knows a chick's chirp
Rewrite 5: could pick him out of a lineup of identical twins
Comment: In the last rewrite, I wanted to use "look-a-likes" for its alliterative qualities, but isn't it redundantc to say "a lineup of look-a-likes"?
More reading about clichés
What I found when I googled "cliches"
• The New Cliché: "It's the Wikipedia of..." at "loose wire" on September 29, 2005, by WSJ online columnist Jeremy Wagstaff.