thimble en matelotage c'est une cosse pour renforcer l'oeil d'un cordage ou d'un fil d'acier.

Probably some type of ferrule, but really need to see it to be sure...

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Note added at 54 mins (2007-09-06 13:16:14 GMT)
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A 'virole' can certainly be large and cylindrical in shape; my biggest concern is that they are usually made by rolling sheet material up and joining the seam, whereas I suspect what you have may be either deep-drawn or machined. Any clues?

In the example below, the two pieces of the thimble are screwed together to form a shell over the cable ends when they are connected. I can see why you were thinking of "douille."

Insert the transducer housing into the cable assembly thimble (knurled assembly). Hold the transducer assembly in one hand and the cable in the other near the thimble. See Figure 3.2 below. While applying slight pressure to push the two parts together, slowly rotate the transducer assembly in the thimble until the keys align. When the keys align, the housing will slip into the thimble assembly an additional one inch and you will no longer be able to rotate the transducer while holding the cable. Now that the keys are aligned and seated, grasp the transducer in one hand and the knurled thimble in the other. While applying slight pressure to push the two parts together, screw the thimble onto the transducer housing. Continue threading the parts together until they are fully mated, leaving no visible gap where the thimble meets the transducer housing.
http://www.psih.com/pdf_files/550_Users_Manual_October_2005....

chaussette, n.f.
Domaine : Ingénierie nucléaire/Technologie des réacteurs.
Définition : Tube étanche fermé à une extrémité permettant d'introduire un objet dans un milieu, sans contact direct.
Voir aussi : doigt de gant.
Anglais : thimble.
http://www.translationdirectory.com/glossaries/glossary018_c...

doigt de gant
Domaine : Ingénierie nucléaire/Technologie des réacteurs.
Définition : Tube de petit diamètre fermé à une extrémité et permettant d'effectuer certains échanges entre des milieux physiques séparés.
Voir aussi : chaussette.
Anglais : thimble.
(Source : arrêté du 30 novembre 1989)
http://www-rocq.inria.fr/qui/Philippe.Deschamp/RETIF/2000092...

DASSAULT AVIATION – Lexique bilingue
DE (DE RACCORDEMENT/BOUT DE CABLE… - THIMBLE
DOUILLE (CARTOUCHE, OBUS) – CASE (CARTRIDGE/SHELL…)
http://www.dassault-aviation.com/services/fr/transverse/lexi...

cartouche d'extraction - extraction thimble (chem)
http://www.techtrans.com.fr/GlossaryEn.pdf