The convex presupposes the concave; and vam is related to vap (as somnus is related to hpnos, to svapnas, and to sopor).
sopor so·por (sō'pər, -pôr')
A deep, lethargic, or unnatural sleep.
A sedative drug, methaqualone; Quaalude2: an apparently insatiable market for the ''sopers''
[1960s+ Narcotics; fr Sopor, the trademark of a brand of the drug, fr the Latin root for ''sleep'']