"By jingo" is an archaic expression meaning "by God" or "by the name of God". Some synonyms for this phrase include "by heavens", "by Jove", and "by the holy rood". These phrases were common in the past, but have fallen out of use in modern times. Other more contemporary expressions that convey a similar meaning include "good heavens", "my goodness", and "oh my God". No matter the phrase used, they all express a sense of surprise or shock and invoke a higher power for emphasis. However, it's important to note that some of these expressions may be considered outdated or inappropriate in certain situations.