Why does my wife go off it when i tap her backside after we make love.it's just two little taps.?

I guess it would depend on how you're tapping her. If it's like when you tap your buddy on his back for a "Hey good job" tap, it's somewhat obnoxious. Also if it's a tap like "ok you can get out of bed now" that's also obnoxious. What does the tap mean? why do you do it? she may not know the 'meaning' and the context may be off, insted of tapping her, why not give her a kiss?