Is "porta8" on f116v a Latin abbreviated word?

[Carnby]

I wonder whether the "porta8" word on You are not allowed to view links. Register or Login to view. is actually a Latin abbreviated word:

The reason is that I found several examples of 14-15th century Latin manuscripts, with this exact word (ending in "8"):

Could someone who speaks good Latin translate what "porta8" could be in these cases? I suspect the "8" is an abbreviation.

Another possibility is that the final sign is a sigmoid (closed) s (ꟙ) rather than an abbreviation mark. In some 14th- and 15th-century cursive hands the two shapes can be similar. In that case, the word would simply be portas.