from Latin vēlōci-, vēlox swift + -ous
1680 - (as adverb, velociously) A Compleat and Compendious Church-History,
1775 - (as adjective, velocious) A Concise Natural History of East and West Florida,
Both are shown below (from E-NED);
I was unable to find the given passage from Romans' book but a different one is shown in the Example below.
An even earlier Example (1660) for 'velocious' is also shown below.
From: A Concise Natural History of East and West Florida
By Captain Bernard Romans
New-York Printed, 1776
From: The Learned Man Defended and Reform'd:
A Discourse of Singular Politeness, and Elocution
Written in Italian by the happy Pen of P. Daniel Bartolus
Englished by Thomas Salusbury
The Second Part