Some fans believed it was because "First he brought the sparkle back to her eyes, then he got it tattooed..." but uh, #NAH.
He actually revealed to fans in Boston that, "Sometimes it feels like she's always watching me."
Less cringe, but still WEIRD.
I guess now that they have a baby Liam misses his wifey and fam a lot more when he is away, so the tattoo may make him think of that.
We're clutching at straws here, all we can confirm is that yes, the tattoo is of Cheryl's eyeball and as per usual, fans knew the truth 3456657 years before it was confirmed.