Some spelling forms (and the existence of the English verb enseam v.) suggest that ensaimer and essaimer1 were confused, even though their meaning is completely opposite.
v.a.
1to fatten:
(
MS: 1155-60
)
Engraissiez est li amez e recalcitrat, engraissiez, esaimez (l. e[n]saimer?), ensampliz (Latin: Incrassatus est dilectus et recalcitravit, incrassatus, impinguatus, dilatatus)274.22
[ensaimer] (c.1145)