Tabernac is one of the worst curse words you can use in French Canada. French Canada has a strong tradition of Roman Catholicism and this sacriligious word takes the word "tabernacle" in vain.
"tabernac' de fou", "c't'une tabernac d'affaire, là"
Fr. Canadian. An expression of surprise, warning ('look out!), astonishment, or disgust. Alternate spelling of tabarnak.
(To a wayward horse from the cart driver.) 'Whoa! Whoa! Tabernac!'