From The Collaborative International Dictionary of English v.0.48 [gcide]:
Gladen \Gla"den\, n. [AS. gl[ae]dene, cf. L. gladius a sword.
Cf. Gladiole.] (Bot.)
Sword grass; any plant with sword-shaped leaves, especially
the European {Iris f[oe]tidissima}. [Written also gladwyn,
gladdon, and glader.]
[1913 Webster]