It is true to some extent for the Latin feminines ending with -io, -tas
Likewise for MoGrSome rules of thumb for the gender of modern loanwords in (European) Spanish:
- Words refering to people take the gender of the given person. For example, samurai is m, geisha is f, or hacker is m or f depending on the gender of the person.
Likewise for MoGr with some exceptions e.g «πιάνο» [piˈano] or [ˈpç͡ano] (pronunciation depends on the region) < Ιt. piano (masc.), which is neuter in Greek, while «ελίτ» [eˈlit] < Fr. élite (fem.), remains feminine.
- Words which come from other Romance languages preserve the original gender (élite f, from French; piano m, from Italian; paella f, from Catalan), with some exceptions (gofre m, from Fr. gaufre f).
In Greek these words are mostly neuter and uninflected e.g. «το μπλογκ» [to ˈblog] (neut. nom. sing.) --> the blog, «του μπλογκ» [tu blog] (neut. gen. sing.) --> of-the blog.
- Words which come from other languages families (especially English) almost always take the masculine gender (fútbol, blog, chat, hobby, email, mitin (meeting, from English; sushi, sudoku, from Japanese...).
Likewise for MoGr, these words are treated as inflected, patterned after existing, inherited, similar-sounding Greek words e.g. «η Μπουντεσλίγκα» [ i bundesˈliga] (fem. nom. sing.) --> the Bundesliga, «της Μπουντεσλίγκας» [tis bundesˈligas] (fem. gen. sing.) --> of-the Bundesliga, patterned after the inflection of the fem. Gr. nouns «λύσσα» [ˈlisa] or «λίγδα» [ˈliɣða] (that's the grammar rule, but unfortunately in reality one ofter hears (especially by "respected" anchormen/-women) on TV solecisms of the kind «η Ευρωλίγκα» [i evroˈliga] (fem. nom. sing.) --> the Euroleague, «της Ευρωλίγκα» [tis evroˈliga] (fem. gen. sing.) --> of-the Euroleague, treating the word as if Greek is an uninflected language).
- Borrowings which resemble existing words in Spanish usually take the gender of it: Bundesliga (liga f) is feminine, newsletter (letra f) vacillates.
The same happens in MoGr.
- Sometimes the current borrowings are abbreviations, like web, which is either masculine or feminine because it can mean both "website" (sitio web) or "webpage" (página web).
«Γκεστάπο» [ɟeˈstapo] is feminine in Greek too, because "Police" = «Αστυνομία» [astinoˈmi.a] is also feminine. The same for «σέλφι» [ˈselfi] = «η σέλφι» [i ˈselfi] (fem.), associated with «η φωτογραφία» [i fotoɣraˈfi.a] (fem.) --> the (fem. def. artcl.) photograph.
- Words like Gestapo are associated to a more general word (policía f), and take its gender (feminine here). Selfie is sometimes feminine because I guess people associate it with foto f.
Words ending in «-α», or «-η» are 99,9% feminine in MoGr. e.g. «η Σαρία» [i saˈɾi.a] (fem.) --> (the) Sharia, «η σάουνα» [i ˈsa.una] (fem.) --> (the) sauna.
- Words ending in -a vacillate (masc: vodka, manga, pijama, burka, karma; fem: katana, sauna, sharia, ikastola). Some seem to be simply random, but others may have some logic behind: manga (cómic m), katana (espada f "sword"), ikastola "Basque-speaking school" (escuela f).
These words in MoGr are taken as stranded adjectives, thus «Ουνέσκο» [uˈnesko] --> Unesco is feminine, «η Ουνέσκο» [i uˈnesko] because the feminine noun «οργάνωση» [orˈɣanosi] (fem.) --> organization, is implied, «ΝΑΤΟ» [ˈnato] is neuter, «το ΝΑΤΟ» because the neuter noun «σύμφωνο» [ˈsimfono] --> treaty, accord is implied etc.
- Acronyms usually take the gender of the most important word: Unesco, OTAN (organización f), sida (síndrome m), PSOE (partido m), CIA (agencia f).
Actually, there's a general tendency in BCS to assign only masculine or feminine gender to loanwords, thus neuter is reserved for "native" words. I can't offhand recall any recent loan which is neuter.