Vaina also means a pod - vainitas are green beans, it's also the root of vanilla - vainilla. Similar to sheath.
Pocket Oxford Spanish Dictionary ? 2005 Oxford University Press:
vaina sustantivo femenino
1. (de espada) scabbard;
(de navaja) sheath
2. (Bot) (de habas, etc) pod
3. (Col, Per, Ven fam)
1. (problema, contrariedad): ?qu? ~! what a drag o pain (colloq);
la ~ es que no s? c?mo the thing o problem is that I don't know how;
estoy metida en una ~ I'm in a spot of trouble (colloq)
2. (cosa, asunto) thing, thingamajig (colloq)
3. (comportamiento sospechoso): ten?an una ~ they were up to something funny;
?qu? ~ te traes t?? what are you up to?
Pocket Oxford Spanish Dictionary ? 2005 Oxford University Press:
vaina sustantivo femenino
1. (de espada) scabbard;
(de navaja) sheath
2. (Bot) (de habas, etc) pod
3. (Col, Per, Ven fam)
1. (problema, contrariedad): ?qu? ~! what a drag o pain (colloq);
la ~ es que no s? c?mo the thing o problem is that I don't know how;
estoy metida en una ~ I'm in a spot of trouble (colloq)
2. (cosa, asunto) thing, thingamajig (colloq)
3. (comportamiento sospechoso): ten?an una ~ they were up to something funny;
?qu? ~ te traes t?? what are you up to?