Langer Name Meaning. German, Dutch, Danish, and Jewish (Ashkenazic): nickname for a tall man, from an inflected form of Lang. According to Gottschald, in the Franconian dialect of German this was also a term for an unskilled laborer (more fully, Handlanger).
Muscle does not weigh more than fat, any more than lead weighs more than feathers. A pound is a pound is a pound. Where the misunderstanding often comes in is that muscle is much more dense than fat, so that, by volume, it seems to weigh more. That is, a pound of muscle occupies less space than a pound of fat. In addition, because a pound of muscle burns more fat than a pound of fat, even at rest, by increasing your lean muscle tissue mass, you're helping your body burn more calories. But back to your question.
Muscle growth comes about because of hypertrophy or hyperplasia. Hypertrophy is an increase in the size of the muscle due to an increase in the size of the muscle fibers, while hyperplasia is an increase in the number of muscle fibers. Hypertrophy comes in two forms, sarcomere hypertrophy, an increase in the size of the contractile portion of the muscle; and sarcoplasmic hypertrophy, an increase in the non-contractile portion of the muscle. Sarcomere hypertrophy involves a smaller increase in the diameter of the muscle, but muscle density increases. Sarcoplasmic hypertrophy shows an increase in muscle diameter and a decrease in density. All hypertrophy will involve both processes; the ratio is dependent on training intensity and frequency.