gerb

/ɡerb/

Cases

SingularPluralWhen to use it
nominativegerbthe coat of armsgerblethe coat of armsesthe plain dictionary form — the doer of the sentence
genitivegerbnithe coat of arms'gerblenithe coat of armses'the owner — whose it is
accusativegerbnithe coat of arms (as the object)gerblenithe coat of armses (as the object)a specific, known object — whom or what
dativegerbgeto the coat of armsgerblegeto the coat of armsesdirection or recipient — to where, to whom
locativegerbdeat / in the coat of armsgerbledeat / in the coat of armseswhere it is; also having — mende bar, "I have it"
ablativegerbdenfrom the coat of armsgerbledenfrom the coat of armseswhere it comes from; also "than" when comparing
When to use each case
nominative
the plain dictionary form — the doer of the sentence
genitive
the owner — whose it is
accusative
a specific, known object — whom or what
dative
direction or recipient — to where, to whom
locative
where it is; also having — mende bar, "I have it"
ablative
where it comes from; also "than" when comparing

The endings are the same ones the pronouns wear — that page explains when each case is used.

With an owner

One ownedSeveral owned
mygerbimmy coat of armsgerblerimmy coat of armses
yourgerbingyour coat of armsgerbleringyour coat of armses
his / hergerbihis / her coat of armsgerblerihis / her coat of armses
ourgerbibizour coat of armsgerbleribizour coat of armses
you all'sgerbigizyou all's coat of armsgerblerigizyou all's coat of armses
theirgerbleritheir coat of armsgerbleritheir coat of armses

The overlap in the last rows is real, not a mistake: gerbleri can mean "his / her coat of armses", "their coat of arms", or "their coat of armses" — context decides.