One of the mysteries of the English language finally explained.
Definition of woo-woo in US English:
woo-woo
(also woo)
adjective
derogatory, informalRelating to or holding unconventional beliefs regarded as having little or no scientific basis, especially those relating to spirituality, mysticism, or alternative medicine.
‘quartz crystals that were so popular with the woo-woo crowd’‘phrases like that will prove a little woo-woo for some readers’
noun
derogatory, informalUnconventional beliefs regarded as having little or no scientific basis, especially those relating to spirituality, mysticism, or alternative medicine.
‘some kind of metaphysical woo-woo’
Origin
1980s: probably in imitation of a wailing sound traditionally attributed to ghosts and humorously associated with mysticism and the supernatural.