The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
dher-
DEFINITION:
To hold firmly, support. Derivatives include infirmary and throne. 1. Suffixed form *dher-mo-.farm, fermata, firm1, firm2, firmament; affirm, confirm, furl, infirm, infirmary, from Latin firmus, firm, strong. 2. Perhaps extended form *dhergh-, seen by some as the source of Latin fortis, strong, but this is more likely from bhergh-2. 3. Suffixed zero-grade form *dhr-ono-.throne, from Greek thronos, seat, throne (< support). 4. Suffixed form *dher-m.dharma, from Sanskrit dharma, statute, law (< that which is established firmly). 5. Suffixed form *dher-eno-.dharna, from Prakrit dharaa, a holding firm. 6. Suffixed o-grade form *dhor-o-.sirdar, tahsildar, zamindar, from Iranian dra-, holding, whence Persian -dr. (Pokorny 2. dher- 252.)