Well, its not a joke, that is the real translation! (and you roll your eyes and say Duh!)
Up until 5 minutes ago, I thought saying "o ou mama na" was more so an encourgament or blessing that was NOT lungs...but rather something more ummm, different.
I went to Tupua Tamasese's speeches (for my weekly motivation) and found that it is a metaphorically signifying the function and importance or your mama:
"Take our lungs which is source and symbol of the breath of life which imparts to you and your mission of love and prayers" (His speech for Albert Wendt on winning Commonweath prize)