^ Sources for this site.
Of course you can't certify any information. But look at whether the authors cite their sources, and whether those sources are academic (either citing primary historical records, or citing other academic authors).
Also look at the purpose of the reference. If it is written purely as a reference, to document name meanings and usage, the author probably put more effort into being accurate. If it's written to help you name a baby and includes a lot of stuff about style and modern context, the author is liable to be more interested in supplying pleasing meanings, without worrying about their accuracy.