In medieval orthography (Latin esp, but scribes used it in other languages*) a macron is a abbreviation of "*n" or "*m". To this very day, doctors indicate "with" on prescriptions by a "c" with a bar over it: "cum". (At least those still writing them out long-hand like the psychiatrist I work with.)

[* I've long surmised the macron is the ancestor of the tilda, and that if you go far enough back in Castilian Spanish, the word for "lord" was spelled "senner" -- double n's being how that sound was previously indicated in Spanish, something I gather has precident in other languages. ]

So that word is "dampum" or "dampen" or some such.