Harmonia Nectere Passus derives from theree Latin words.
"Harmonia" means "harmony", which is ultimately derived from the Greek verb ἁρμόζω (harmozō) which means "I fit together". (It could be either in the nominative or ablative case, denoting the subject or the means.)
"Nectere" is a verb meaning "to connect, join, or bind". (It is probably an infinitive, but could also be a passive imperative.)
There are multiple possible meanins of "Passus." It could be a noun meaning "step." (It could be singular or plural, as they are spelled the same even though the second vowel is pronounced differently in the plural.) The full incantation could mean "to join steps in harmony."
It could be the past participle of the verb "pando," meaning "having spread, opened, unfolded, or extended." (The noun for step is ultimately derived from this.) The full incantation could mean "when opened, be joined in harmony."
It could also be the past participle of the verb "patior," "having suffered, endured, submitted, or allowed." The English words "passion" and "sympathy" derive from this. The full incantation could mean "allowed to join in harmony.
Any of these options would still describe the binding of a rift between the sister Vanishing Cabinets.
Behind the scenes
- Harmonia Nectere Passus is one of the only four spells known to have three words to its incantation, the other two being Petrificus Totalus Duo, Tria and Accio (sometimes).
- Harry Potter and the Half-Blood Prince (film) (First appearance)
- Harry Potter and the Deathly Hallows: Part 2 (Appears in flashback(s))