In regard to Greece, cant answer the Russian one..
But the Greek and Roman soldiers supposedly were encouraged to  have a more than standard form of closeness if you will.
It was thought that youd fight harder to protect your lover so sodomy and what we now consider gay relationships were encouraged amongst them even tho many were married with children.

I am bisexual myself so I have no issues with anyones sexual orientation..

But at any rate the term supposedly comes from their love of sodomy during that time period.

Dont know how correct that explantion truly is.

xoxo

Storm

Little Neddie don't you ever remember what I taught you...

silly goose! I guess maybe I will have to teach you again about the term "Greek" hahahaha....

Read it somewhere that way back when in Greece the men wanted to marry virgins but wanted to have sex whether married or not. They simply decided that anal would keep the unmarried lady a virgin and "Greek" was born. At least in regard to how the term Greek came about.
Don't know about Russian.
Most likely none of this has anything to do with the truth.
Just like the French Horn isn't French and the English Horn isn't English

Never leave your buddy's behind