This just shows yet another Indo Europeans spreading out from a common root, which the modern scholars have tough time locating to a physical place.
Prem - to love, to show love.
Lila - is the act, the play.
missing "r" just shows the westerners had a tough time sounding "cereberal sounds" where the toung has to curl up and touch the palate. In Sanskrit, we have 5 + 1 sounds, and only "r" has survived as semi-vowel as part of the semi-vowels, "y", "r" "l", and "v"(one cal also include "h". which is spoken soft stop and counter part to "ah", which is visarga, the unspoken hard stop).
Hypothetically - and not really correct - if "a" is a hard vowel, then "ah" can be taken as hard aspirated vowel, then "h" can be taken as soft (semi) vowel, and "hh" can be taken as aspirated soft vowel - but in reality we taken "a" as a soft vowel and do not have "hh" as any vowel.
So "a" is kept seperate, and "ah" and "h" are taken as counter parts, one as "visraga" hard aspirate and the other as "h" soft aspirate, even though "a" is taken as a soft vowel and removed from the pairing.
Further "ah" can become "aR", "aS", "as" and "ach" sounds when following Sandhi or Phonetics Combination Principles of Sanskrit Sounds.