The secret sniff is a sexual technique that has evolved over the years to prevent the unfortunate situation of fellatio on a less-than-ripe vagina.
To perform the secret sniff, one most slowly and carefully start the oral foreplay somewhere in the region of the woman's bosom. Whilst moving south towards the area of the subject's fertility field, one should then start a process of subtle nasal inspection. The secret sniff is just that, a quiet, inconspicuous, drawn out sniff that if done properly would alert the oral giver to a potentially undesirable vagina. In extreme cases, the smell can be picked up as far away as the woman's neck. Legend has it that a poor male once had unintentionally performed a secret sniff from across a bedroom, leading him to down a jamo and proceed directly to rushed sex.
Poor Dave, I heard he had a cold last weekend and was unable to pull the good ol' secret sniff on that slut he picked up. He said food tasted like spoiled sea bass for a week