Translation:If I had a nickname, I would be happy.
You probably mean maljuna, the opposite of young. Malnova is old as in the opposite of new.
For example, if someone bought a kitten a while back and now buys an older adult cat, then the adult cat would be la maljuna nova kato, while the kitten would be la juna malnova kat(id)o.
I respectfully disagree! A yearning for an identity is a complex human need. Knowing your name is one thing, but a name that shows who you are on the inside is profoundly poetic
I'm not sure that many nicknames really show who you are on the inside in any sort of profound way. They're just as easily taken from some aspect of your appearance, for example.
This is not that kind of nickname. (that would be kromnomo, an "instead name") Kaŝnomo comes from kaŝi (to hide) + nomo (name), so it's a name you use so you don't have to use your real name.
It's also a synonym of the word pseŭdonimo, although that is more specifically "kaŝnomo de verkisto aŭ artisto", according to PIV.
According to the same source, kromnomo is quite specific to the Roman empire citizens: > kromnomo ♜ La tria aŭ kvara nomo de Roma civitano, esprimanta origine personan distingon (ekz. Cicerono, Afrikano ktp); ☞ alnomo, kaŝnomo.