I hear this phrase a thousand times a day. It translates into "let's pretend that", of course. Like Hondo Crouch's "pliking", it's the signature phrase of an overactive imagination. The boys are constantly other people; they try on different identities more often than Imelda Marcos tried on shoes. Current favorites are Revolutionary War patriots, Vikings, pirates, WWII soldiers, and animals of all kinds. They repeat the phrase over and over throughout their games, as they write the script for each other.
"Ten' that I say to you ..."
"Ten' that you say ..."
"Ten' that we grab our rifles and run out the door."
"Ten' that the bad pirates start firing at our ship."
And on and on and on.
As they play they work out their relationship with one another and they work out how they would deal with certain situations. Not that they are likely to face an invading Viking horde anytime soon, but they will face times when they have to make quick decisions, and their play helps them practice that skill. It also helps them to do so cooperatively - they are playing together, and they constantly ask each other for help. That's a skill they need to learn most of all - to turn to one another, grab hands, and face what's coming side by side.
This imaginative play that all of our children engage in helps define who they are and who they will be. The more our children "ten' like" together, the better the understanding they will have of themselves as they grow up.