a welcome, rousing if not always sincere US, 1873.
2
on the railways, the metal air hose coupling between carriages. The interlocking connectors vaguely resemble hands clasped in a handshake US, 1975
the glad hand
The act of addressing one in a friendly manner, often when it is feigned or false. I don't think she actually likes me, so she must have given me the glad hand when she seemed so happy to see me.
*glad hand
Fig. an overly friendly welcome; a symbol of insincere attention. (*Typically: get ~; give someone ∼.) Whenever I go into that store, I get the glad hand.I hate to go to a party and get the glad hand.
glad hand
A warm and hearty but often insincere welcome or greeting, as in Politicians are apt to give the glad hand to one and all. [Slang; late 1800s]