There is no strict grammatical rule governing whether "Lake" precedes or follows the proper name. The convention is largely a matter of historical usage, regional tradition, and the lake's prominence.
Well-known, historically significant, or very large lakes often place "Lake" first:
This form often omits the definite article "the" and emphasizes the lake as a singular, renowned entity.
Smaller, lesser-known, or man-made reservoirs frequently place the name first:
Usage is idiomatic. Major natural lakes tend toward "Lake [Name]"; many reservoirs and minor lakes use "[Name] Lake." Both are correct; local custom prevails.