noun
giving it a try since there's nothing to lose
Colloquial abbreviation of 駄目で元々 (dame de motomoto), meaning 'it was no good from the start, so trying won't make it worse'. Used when attempting something with low expectations, knowing that failure leaves you no worse off.
See also: 駄目で元々
ダメもとで彼女に告白してみた。
I asked her out on the off chance, figuring I had nothing to lose.
ダメもとで応募したら、意外と
I applied just in case, and surprisingly I got accepted.
The full phrase from which ダメもと is abbreviated. More explicit and slightly less casual.
Abbreviation of the phrase 駄目で元々 (dame de motomoto), literally 'no good from the start'. The もと part comes from 元々 (motomoto, 'originally').