Why did my doggie lick the air when I scratched her tail?

Factual Questions
1

I’ve been missing my doggie, who has been dead for more than 15 years now.

One thing I recalled is something she would do very frequently. When she was lying down and indicating that she wanted to be scratched, when I got down to her lower back and the base of her tail, she would get very very still and her tongue would start “licking the air,” in a way that seemed like it was an automatic response.

I wondered if she might be experiencing discomfort, but if I stopped, she would let me know to keep doing it. So I’m assuming it was pleasurable in some way.

So what was that reaction? Was it like purring? or maybe like giggling when being tickled?

2

It’s not an uncommon reaction.

Not every dog does this, but the majority, in my rather extensive experience, do. Both male and female.

It certainly seems to be a sign of pleasure.

3

Never met a dog that didn’t love the butt scratch.

4

Behavior perhaps related to their Jacobson’s Organ?