Figarland Garrick.
"Shanks" was most likely the name that was given by Roger, the name that Garling assigned him at birth, assuming he's the biological dad here, was most likely something else entirely.
But the question would then be what that name is, well I think the answer to this question is already clear to us, you see Oda sometimes gives children names similar sounding to the ones their parents have:
• Spandam -> Spandine
• Ussop -> Yassop
So Oda might following this trend with the names of Garling and his son, hence you'd have Figarland Garling and Figarland Garlic, given the whole thing with "Rs" and "Ls" sounding similar in Japanese, Oda might try to incorporate that into the naming scheme for Garling's son.
Hence giving us the name 𝐒𝐚𝐢𝐧𝐭 𝐅𝐢𝐠𝐚𝐫𝐥𝐚𝐧𝐝 𝐆𝐚𝐫𝐫𝐢𝐜𝐤, plus another reason why this fits aside from the similarity in parent-child names, is because Shanks' rival was Mihawk who is specifically designed after Dracula, this is significant since garlic is said to be the weakness of vampires, so you'd essentially have a guy who's modeled after a famous vampire having a rival whose name is literally Garlic. If that isn't poetic, I don't know what is.