I've known for a while what the word "совсем" means, but only recently did I realize that the meaning stems from the fact that: "совсем = с(о)+всем" (entirely=with everything).
This is probably fairly obvious for native speakers, but it took a long time for me to realize. The same is true of "сейчас = сей+час" (now=this hour/time). Also "нет+(genitive)=не+есть", "когда=кого+года", "всегда=все+года", and "если=есть+ли". There are other such examples which I am forgetting now.
Is there a list somewhere of such common words which are actually built up from small words whose meanings are easier to remember? I feel like this would be very helpful to those learning the language.