The Gaelic word for the kilt is “Feilidh Beag” (small plaid or blanket ) or in the case of the Belted Plaid “Feilidh Mór” or “Breacan An Feile” (seen in “Braveheart).
The word “Kilt” is Scots and (probably) comes from the Norse worde “Kjalta” (to wrap).
From the same root comes “Kjortel” (the type of tunic worn by many people including the Norse).
In Scandinavian languages you have the Danish “kilt” (to tuck), the Swedish “kilta” (to wrap or swathe) AND the swedish and Danish “Kjol” witch in Norwiegian is called “skjört” and Icelandic “skirt” (pronounced “skeert” but with the same meaning as the English “skirt”).
Also, the the Swedish word for the tunic that is part of Sami folk costumes is “kolt”.
The Celts where known to wear trousers (called “bracae” by the Romans).
The Scoti (Gaels) that came to Scotland from Ireland also wore trousers, so did the Gaels in Ireland.
However, male “kiltlike” garments can be found in many cultures (Romans often wore tunics (the word Tunica is Latin) with or without trousers and the Toga is a fabric wrapped around the body. Egyptians also had a garment similar to the modern smaller kilt.
So is the Kilt a Skirt?
Etymologically there is a connection to skirts, tunics and fabrics being “wrapped” around you in general so i would say yes.
Practically, all kilts (great or small) are “wrapped” around so again, yes.
Is it Norse?
Probably, though it might have been worn with a tunic and / or trousers and it would have resembled the great kilt / belted plaid thrown over the shoulder or over the head as a cloak. Though probably not with anything like a tartan.
Tartan came about by weaving as different colours blend you get a tartan / plaid pattern.
Originally tartans where regional. Some dyes where more common than others in different areas, the rest was up to personal taste.
The idea of tartans strongly connected to certain clans , septs or families came later as part of Victorian romanticism.
Is it masculine?
Etymologically all fabrics wrapped around you are connected (Kjalta) regardless of whom it is wrapped around.
The Scottish kilt however is a male garment.
It is however part of the wear of certain dances and in those it is worn by both men and women (in other dances the women wear a tartan dress with a vest called an “Aboyne”).
Traditionall costumes like the Bonnie Prince Charles ,Montrose Doublet or Argyle are usually only worn by men (they all include the kilt).
In todays fashion anyone can wear a kilt that feels like it with or without tartan.
It can be combined with anything one likes and actually that is the most traditional since it did start out as everyday wear.