The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
dher-
DEFINITION:
Under. 1a.under, under-, from Old English under, under; b.U-boat, from Old High German untar, under. Both a and b from Germanic *under-.2.inferior, from Latin nferus, lower. 3.infernal, inferno, from Latin nfernus, lower. 4. infra-, from Latin nfr, below. (Pokorny dhos 771.)
dher-
nferus, lower. 3. infernal, inferno, from Latin 
, below. (Pokorny 
