Last night I worked on a fun song from the 14th C. 'Red Book of Vermell'. I know the general meaning, but I would like to know what each Latin word means. I can guess much of it.

I'm putting the words below, and where it is blank after the dash, I would appreciate it if someone who knows Latin would tell me what that word means.

Laudemus - we praise

virginem - the virgin

mater est - who is mother

et - and

ejus - ?

filius - son?

Ihesus - Jesus

est - is

Plangemus -

scelera

acriter

Sperantes - hope?

in Ihesum - in Jesus

jugiter -

Also, how do I say 'scelera'? (This would be medieval Latin.)

My gang will love this piece, which is a three-part round sung by pilgrims on their way to Santiago in Spain during the middle ages.