Can 'Reticent' Be Used to Mean 'Reluctant'?
The word reticent is a Latin borrowing of the early 1800s. It comes from reticēre, meaning "to keep silent," and was ushered into English with a meaning of "inclined to be silent or uncommunicative." It was used by the likes of George Eliot and Ralph Waldo Emerson to describe those reserved folk who keep mum when others might yammer on—or even just mutter a word or two—about something.
Within 50 years, the word had started to develop a broader meaning. Instead of just describing those who are reluctant to speak, it was being used to describe those who are just plain reluctant. Usually, though, the idea being communicated was the same as with the original use: phrases like "reticent to give information" and "reticent about speaking of it" maintained the "inclined not to talk" meaning.
Reticent meaning "hesitant" or "reluctant" is most frequently followed by "to" and a verb. In the early part of the 20th century reticent to wasn't all that common, and when it was used it was followed by verbs that preserved that original "inclined not to talk" meaning, like discuss and talk. Or it was followed by no verb at all, as in phrases like "reticent to a fault" or "reticent to us." But as the 20th century wore on, the use of reticent to mean "hesitant" increased, and by the 1940s reticent to was increasingly being followed by verbs like accept, participate, and commit.
When reticent means "reluctant" or "hesitant" today, it often does so in the context of reluctant communication of one kind or another. The use is fully established, though, for other contexts too.
Another note: reticent developed another meaning around the same time as the "reluctant" one, but it doesn't seem to bother anyone. The "restrained in expression, presentation, or appearance" meaning is also fully established. Some people like to use it to describe wines that haven't matured enough to speak their full aromatic minds yet.