There are several different original Japanese abilities that are all translated as 'Maelstrom' in English. The first of these is 水磨龍穴 [suima ryuuketsu] or 'water polish dragon hole' in Japanese, and originates in FF Tactics. The second and third are quite similar, and are メイルシュトローム [maelstrom] and メイルシュトロム [maelstrom] in Japanese.
Final Fantasy V
Effect: magical damage, reduces HP to single digits
Targets: all enemies or all allies
Usable: ?
Final Fantasy XI
Type: Blue Magic, MP: 162, BMP: 5
Learn at: BLU 61
Casting: 6 s, recast: 39 s
Stats: MND +2, Type: ?
Learn from: Bathybic Kulushedra, Blanched Kraken, Charybdis, Colossal Calamari, Dalham, Devil Manta, Fe'e, Flying Manta, Glyryvilu, Honor, Kraken, Kulushedra, Lahama, Lord of Onzozo, Morgawr, Ocean Kraken, Peg Powler, Proteus, Sea Bishop, Sea Bronze, Sea Horror, Sea Monk, Tros, Valor
Other: Deals water damage to enemies within range. Additional effect: STR Down
Other: メイルシュトロム in Japanese
Final Fantasy Tactics
Type: Sky Mantra, Element: Magick / Water, MP: -
Target: any, Range: 4 horizontal, any vertical, Radius: 2 horizontal, 3 vertical, Power: 14
Speed: 6 tics, Duration: -, Line of Fire: No
Learn: Skyseer (400 JP)
Incantation: "Man-eating fiend, shake the rain water and tear it up with those claws… Maelstrom!"
Effect: A Water element Magick attack. Hits 1-10 times on random tiles within radius.
Other: Damage = 0.5 x Mag ATK x (Mag ATK + 14)
Other: 水磨龍穴 in Japanese
Airborne Brigade

R+
Type: INT, Element: -, Growth: Slow, Cost: 16
Attack: 1,330 (lv1), ? (lv80), 7,648 (lv100), ? (lv120), ? (lv140), 14,190 (lv160)
Defense: 1,390 (lv1), ? (lv80), 7,467 (lv100), ? (lv120), ? (lv140), 13,760 (lv160)
Obtain: ?
Other: メイルシュトローム in Japanese
R
Type: INT, Element: -, Growth: Slow, Cost: 12
Attack: 940 (lv1), ? (lv60), ? (lv75), ? (lv90), ? (lv105), 8,970 (lv120)
Defense: 1,000 (lv1), ? (lv60), ? (lv75), ? (lv90), ? (lv105), 8,490 (lv120)
Obtain: ?
Category: Ability