The syllable 'op-' may be the stem for Ops, the wife of Saturn in ancient, classical Roman mythology. Or it may be the prefix to Latin nouns and verbs. The form 'op-' is the form of the prefix when it's added to the beginning of nouns and verbs that begin with the letter 'p'. The form 'ob-' is used in front of all other letters. The word 'ob' also is a preposition of the same meaning: 'because of', 'before', 'in front of', 'in return for', on account of', 'to the purpose', or 'towards'.
Opus is Latin for "work".
The Latin word for work is "labor" or "opus."
The Latin word opus translated into English mean deed or labor.
Opus.
opus
domus opus
Opus Christi.
Magnum Opus.
A musical work.
operation, optional
There isn't a specific word for 'firework' in Latin, but if you divide it into 'fire' and 'work' you'll get 'ignis opus'.
The word 'labor' is as much a real word in Latin as in English. In the ancient, classical Latin of ancient Italy, the word means physical work. The word 'opus' also is as much a real word in Latin as in English. In Latin, it's used specifically to refer to the material fruit of physical work.
The usual expression is simply "Opus est" (It / that is needed), as pronouns such as "id" (it) are usually omitted in Latin, because they are redundant with the tense of the verb.