Can "less" means "else"? [closed]

Solution 1:

The word you are thinking of is "lest", not "less".

Google's dictionary says:

• with the intention of preventing (something undesirable); to avoid the risk of. "he spent whole days in his room, headphones on lest he disturb anyone"
• (after a clause indicating fear) because of the possibility of something undesirable happening; in case. "she sat up late worrying lest he be held up on the way home"

Similar: in case, just in case, for fear that, in order to avoid, to avoid the risk of

Interestingly, in its original Old English form "lest" did include the word "less":

"thȳ lǣs the" (whereby less that)  →  "the læste"  →  "lest".

In Old English syntax your statement would have been something like: "He doesn't want to overdo it, thereby less that it ends up backfiring".