It's not perfect, but depending on your definition of "tooltip", this script should dump its name to the chat if you run it while it's visible.
Lua Code:
/run local f=EnumerateFrames()while f do if(f:GetObjectType()=='GameTooltip'or strfind((f:GetName()or''):lower(),'tip'))and f:IsVisible()and f:GetPoint()then print(f:GetName())end f=EnumerateFrames(f)end