bulwark (noun) - a defensive wall, rampart, or breakwater; any source of strong support or protection [buhl-werk]
a boulevard is a wide street, typically lined with trees
BREAKDOWN: The word bulwark derives from classic roots but not in an obvious way:
BUL- (to swell or blow) + WORK- (work)
This bole-work describes a palisade or rampart of logs used to fortify or defend. Over time, the word acquired a more general connotation of source of support or strength. Interestingly, the word boulevard is a French variant of bulwark meant to describe a broad street built atop atop demolished city walls or a military fortification.
“The freedom of the press is one of the great bulwarks of liberty, and can never be restrained but by despotic governments.” —George Mason

[Our Wednesday Wildcards are fascinating and important words that are not derived from classical roots.]