The phrase "strong right arm" refers to someone who is dependable and reliable. However, there are several synonyms that can be used in place of this phrase to add variety to one's writing. These synonyms include "stalwart," "support," "mainstay," "dependable," "reliable," "backbone," "pillar," "foundation," "cornerstone," and "crutch." Each of these terms conveys the idea of someone or something that provides strength and support. When used in written or spoken language, these synonyms can help to add depth and nuance to one's writing or speech.