In the 100 TV series, we hear word "heda" or "one heda" a lot from grounders. It would make sense to mean something like leader but I've came across threads arguing that it means more than that.
So what exactly does "heda" mean?
Heda is TRIGEDASLENG for leader or commander. It is the Grounder code/slang language that was developed after the war, mainly to hide from the mountain men. Heda comes from English 'head' and the suffix 'er' (often changed in slang to 'a'). Similar to modern English slang where someone heads up a team.
As was already pointed out that Heda translates to leader or commander, I wanted to add that we hear this used to refer to Clark when she gets the nickname 'Wanheda' post Mount Weather incident.
Wan presumably means death and heda means commander as the nickname translates to "Commander of Death".
heda means commander it's the leader of all grounders even back When the collation didn't exist so basically the commander was leader over a bunch of squabbling tribes before lexa united them and became the first commander to rule over the united twelve clans hence why they call her Heda Lexa commander of the twelve clans