From Middle Dutch rammeken (“toasted bread”) or Middle Low German ramken (“cream”), from rame, rōme (“cream”), from Old Saxon *rōm (“cream”), from Proto-West Germanic *raum, from Proto-Germanic *raumaz (“cream”), from Proto-Indo-European *rewǝgh- (“to sour”).
Cognate with Old High German roum (“cream”), Old English rēam (“cream”). More at ream.