encaquer

Literally to pack herring into a caque (barrel) for salting or smoking, and by extension, familiarly, to cram people or things tightly into a small space (encaquer des passagers dans un compartiment) — a vivid, faintly archaic image of tight packing.

• Les pêcheurs encaquaient les harengs dès leur retour au port. — The fishermen packed the herring into barrels as soon as they returned to port.
• On nous a encaqués dans un wagon bondé. — We were crammed into a packed train car.
• Ce mot évoque l'image de sardines encaquées les unes sur les autres. — This word evokes the image of sardines packed tightly on top of one another.

Rare and slightly archaic outside its figurative 'crammed in' sense — entasser is the everyday word for packing people or things tightly.

• expression "La caque sent toujours le hareng" — A traditional French proverb, rooted in the herring-barrel trade the verb encaquer comes from, meaning someone's true nature or origins always show through eventually — roughly 'a leopard can't change its spots.'