In looking at the roots of these words I came across a couple of sidebar points of interest:

Appendix I
Indo-European Roots

ENTRY: eis-
DEFINITION: In words denoting passion. 1. Suffixed form *eis--. irascible, irate, ire, from Latin ra, anger. 2. Suffixed zero-grade form *is-()ro-, powerful, holy. hieratic, hiero-; hierarch, hierarchy, hierodule, hieroglyphic, hierophant, from Greek hieros, “filled with the divine,” holy. 3a. iron, from Old English se(r)n, ren, iron; b. gisarme, spiegeleisen, from Old High German sarn, san, iron. Both a and b from Germanic *sarno-, “holy metal” (possibly from Celtic). 4. Suffixed o-grade form *ois-tro-, madness. estrus; estrogen, estrone, from Greek oistros, gadfly, goad, anything causing madness. 5. Suffixed form *eis-mo. Asmodeus, from Avestan ama-, anger. (Pokorny 1. eis- 299.)


The American Heritage® Dictionary of the English Language, Fourth Edition. Copyright © 2000 by Houghton Mifflin Company. Published by the Houghton Mifflin Company. All rights reserved.

So would an iron cross, subject to rusting holes, be the ultimate in irony?

And oestrogen is linked to gadfly and mad behaviour - hah, so it's true! ;)