When I first heard this phrase as a teenager (late 90s/early 2000s), it was being used to describe sycophantic talk or fulsome praise of someone. At the time, I figured the phrase originated as a comparison with the way a dog might lick its master profusely when it is scared or wants something. I haven't used this phrase in a long time, and recently, I used it. I suppose it's an unfortunate consequence of living in a hypersexualized era, but a while after the conversation, I got to wondering if I should have used that phrase (I was talking to someone older, whom I respect), because it might have a connotation that is quite different from what I originally thought.
Edit: Prompted by Jason Bassford, here is a relatively recent example used by a well-known online publication, The Huffington Post:
All The Hard-Hitting Questions Sean Hannity Asked Donald Trump At A ‘Town Hall’ This Week - In which we watch a televised tongue bath so you don’t have to.
Among mature, educated speakers, does this phrase have any vulgar or sexual connotations?