If one reads the Nordiac Languages, one would get a feeling that one is reading Sanskrit-like language. And this is not a surprise considering Indo European Language, Culture and Religion belongs to the same stock of ancestors.
Martti Ahtisaari - Mar + t + ti + A + ha/hi + ti + saari
Mar - Root is "mR(i)" - To Die. Next grade sound makes it "Mar" - which is the Guna grade.
Mar + t => Makes it Active Present or Passive Past Participle (there are some subtle rules to make it different but we can not be sure here there is some corruption going on).
Mar + t + t -> Sometimes the consonants get doubled.
Mar + t + t + i -> Makes in Locative with meaning of "in" or "on". So it means "In or On Death".
a = Prefix used for making a consonant word with negative meaning.
hati -> hurt, inhured, blemished, defeated
hit -> purpose, proper, beneficial, advantageous, friendly, pleasant, protected, running, speeding, set up, planned, prepared, held, assigned, reckoned, constituted, appointed, given, salutary, agreeing, wholesome, convenient, suitable, and useful.
saar - saar -> essence, full of, like "ness".
saar + i - one in tht essence of something.
So it means, "one in death, one who is in full of, either not defeated, hurt, blemished, ..., or not with purpose, beneficial, ....
I will choose to go by the word "hati" as it agrees with spelling and also has some positive context.