ETYMOLOGY
from dure (to last, continue in existence) + -ful
EXAMPLE
“… Be nought dismayd that her vnmoued mind,
doth still persist in her rebellious pride:
such loue not lyke to lusts of baser kynd,
the harder wonne, the firmer will abide.
The durefull Oake, whose sap is not yet dride,
is long ere it conceiue the kindling fyre:
but when it once doth burne, it doth diuide
great heat, and makes his flames to heauen aspire. …”
From: Amoretti vi, in Amoretti and Epithalamion
By Edmund Spenser, 1595
Lexicophilia 