The Pronunciation and History of Interesting

There are a number of ways to say interesting. It can have three syllables or four; it can have an accent only on the first syllable, or it can also have a secondary accent on the "res"; the first "e" can get ignored, resulting in a second syllable of "tres" rhyming with dress; or the second "e" can be ignored, resulting in a syllable that sounds like terse. All of these various pronunciations are well-established and occur in the speech of educated, native speakers of English.

The word interesting originally meant "of concern"; it was a synonym of important. It comes from the verb interest, which in its original use meant "to induce or persuade to participate or engage." If you were interested in something, you were not willing to be a bystander; you felt the need to participate or engage.