pennywhistle vs fipple flute

pennywhistle and fipple flute both are nouns.

Word	Noun	Adjective	Verb	Adverb
pennywhistle	Yes	No	No	No
fipple flute	Yes	No	No	No

As nouns, fipple flute is a hypernym of pennywhistle; that is, fipple flute is a word with a broader meaning than pennywhistle:

pennywhistle: an inexpensive fipple flute
fipple flute: a tubular wind instrument with 8 finger holes and a fipple mouthpiece

Other hypernyms of pennywhistle include fipple pipe, recorder, vertical flute.

pennywhistle (noun)	fipple flute (noun)
an inexpensive fipple flute	a tubular wind instrument with 8 finger holes and a fipple mouthpiece