Well before the fasting of Ramadan was revealed the Messenger of Allah (peace be upon him) used to fast 'Ashura' and 3 days of each month.
Narrated `Aisha: The people used to fast on the day of 'Ashura' before
fasting in Ramadan was prescribed but when (the order of compulsory
fasting in) Ramadan was revealed, it was up to one to fast on it (i.e.
'Ashura') or not.
[Sahih al Bukhari]
Ramadan رَمَضَانَ as a month was called in the jahilya at first taatal تاتل (means a person who gets/tufts water from a source or a well) (Here's my Arabic source other names are also quoted there see also in Wikipedia) ... then about 200 years before Islam they renamed it Ramadan according to a proposal of Kelab ibn Murra كلاب بن مرة because Ramadn then was at the beginning of the summer heat which explains the relationship to the word "ar-Ramda'"الرمضاء so in Arabic it's still said رمض الصائم يرمض if one's stomach gets "hot" because of the big thirst while fasting!
According to some ahadith (hadiths) mentioned in Tafsir ibn Kathir about the Verse in Surat al-Baqara (2:185) all the holy books of the other prophets have also been revealed in Ramadan.
About fasting before Islam i found the following
'Abdullah bin 'Amr (May Allah be pleased with them) reported: The
Messenger of Allah (ﷺ) said, "The Salat which is dearest to Allah is
that of (Prophet) Dawud; and As-Saum (the fasting) which is dearest to
Allah is that of (Prophet) Dawud. He used to sleep half the night, get
up to perform Salat for one-third of it, then sleep through the
remaining one-sixth of it; and he used to observe Saum on alternative
[Al-Bukhari and Muslim]
According to this article some people in Jahliya used to fast A'shura' and used to do good things during Ramadan it also pretends that the sabi-a (mentioned in for example in Surat al Baqara (2:62) see below) used to fast one lunar month as we do (moonsighthing, duration, and rules of fast)
Rest assured that whosoever from among the Muslims or the Jews or the
Christians or the Sabaeans believes in Allah and the Last Day, and
performs good deeds, he will have his reward with his Lord and he will
have no cause for fear and grief
And Allah knows best