From Wiktionary, the free dictionary
ô (“umbrella”) + dù (“umbrella”). To defend someone could be thought of as using umbrellas to shield them.
ô dù
- (literal, collective) all kinds of umbrellas
ô dù
- (informal, derogatory) prone to defending or shielding your allies from scrutiny or criticism
Cần tránh tật bè phái, ô dù.- One needs not form cliques or have too much group identity.