Strong’s Greek
G1619 — ektenos
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
ἐκτενῶς
ektenos — pronounced ek-ten-oce'
adverb from 1618; intently:--fervently. see GREEK for 1618
1 occurrence in the KJV.
1 Peter 1:22
Seeing ye have purified your souls in obeying the truth through the Spirit unto unfeigned love of the brethren, see that ye love one another with a pure heart fervently: